The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
With the increasing requirements for energy saving and emission reduction, as well as air pollution control, new energy vehicles are gradually being promoted and applied in the market, and electric vehicles are the main force of new energy vehicles. A vehicle-mounted charger is an important part of an electric vehicle. The vehicle-mounted charger generally has an AC input terminal and two DC output terminals. The AC input terminal is connected to the mains network; the first DC output terminal charges a high-voltage battery and thus is equivalent to a main circuit output; the second DC output terminal supplies power to in-vehicle electrical devices and a low-voltage small battery and thus is equivalent to an auxiliary circuit output. In the traditional transformer integrated multi-port power output, the problem of automatic power distribution, i.e., the problem of output power cross adjustment, is encountered. The effect of this problem is that the output power of the main circuit will affect the output power of the auxiliary circuit at the same time. For example, when the output power of the main circuit is at a small load or no load (equivalent to that the high-voltage battery at the first DC output is about to be full or already full), a master controller will issue a small duty cycle and even enter into an intermittent operation mode, and in this case, the magnetic flux in a transformer is very small, or almost zero, the induced voltage on the winding of the auxiliary circuit will also be zero. If the auxiliary circuit requires a large output power (equivalent to using a vehicle-mounted electrical appliance in the vehicle), the situation that output power cannot meet use demands will happen.
Therefore, it is desired to design a control method that can stabilize the magnetic flux in the transformer when the main circuit output is at a light load and no load, so that the auxiliary circuit can normally draw electric energy from the transformer, and conversion direction of the power in each port and the number of conversions can also be controlled conveniently.